This tester is a must for preventing accidental choking. If an object fits completely inside the tester, it's small enough to be a hazard.
Allen Company Choke Tube Vials, 12-Gauge Chokes
Beckers
Performore Choke Tester for Small Objects Choking Hazards for Children, Anti-choking Hazard Device for Kids, Home Safety Portable Tube Cylinder Tester
Briley MFG - Companion Drop-In Tube Set, Standard Weight COMPLETE SET
Shotgun Choke Tubes Guide for Hunting and Shooting
No Choke Tube - Set of 3
No Choke Tube - Set of 3
Energy Stick® Science Kit - Steve Spangler Science
Choking Tungsten - Wildfowl
Carlson's Extended Complete Waterfowl Choke Tube Set Browning